Various gypsum products, including wall panels, ceiling panels and tiles, are commonly used in the construction industry. Many of these gypsum products are made by preparing an aqueous gypsum slurry with calcined gypsum (calcium sulfate alpha hemihydrate, calcium sulfate beta hemihydrate and/or calcium sulfate anhydrate), shaping the slurry and then allowing the slurry to harden by rehydrating calcined gypsum into gypsum (calcium sulfate dihydrate).
Gypsum panels can be manufactured by sandwiching a gypsum slurry between two cover sheets known as facers. In some applications, a facer is a paper sheet. Such wallboards in which a gypsum slurry is sandwiched between two sheets of paper find many different applications in building construction. However, wallboards may be sensitive to moisture and at least in some applications, other facer materials such as fibrous mats can be used as described for example in U.S. Pat. No. 8,329,308 and US Patent Publication 2010/0143682, both to the United States Gypsum Company, and the teachings of which are incorporated herein by reference. Suitable fibrous mats further include those disclosed in U.S. Pat. No. 5,772,846 and which are made with glass fibers and polyester fibers bound together.
US Patent Publication 2011/0086214 laminates one of the glass mat surfaces with a stiffening layer before the mat can be used in making a gypsum product. US Patent Publication 2002/0187296 discloses an assembly line on which a glass fiber mat is vibrated so that voids in the mat are more evenly filled with a gypsum slurry. U.S. Pat. No. 4,948,647 discloses gypsum products with a laminated composite facing of an outer nonwoven fiber mat and an inner woven fiber scrim bound together by an acrylic film. U.S. Pat. No. 6,524,679 discloses gypsum boards with face sheets comprising glass fibers and a combination of set gypsum and polymeric compound. Finally, U.S. Pat. No. 5,837,621 discloses glass fiber mats coated with at least one nitrogen containing compound.
While gypsum panels made with glass fiber mats have many advantages, one of the disadvantages is the resulting boards may have a relatively rough surface. As shown in micrographs of FIGS. 1A-1B, with FIG. 1B being a micrograph with a larger magnification, the surface finish of a typical fiber glass mat made with 1 inch glass fibers can be characterized as rough. When this glass fiber mat is used for making gypsum boards, wrinkles develop during the curing stage and the local variations in the form of hills and valleys on the fiber glass mat can be easily seen on the board surface shown in FIGS. 1C and 1D, with 1D being a micrograph taken under a larger magnification. However, it is desirable, especially in connection with interior designs, to obtain gypsum boards with smooth surface.